The present invention relates to a thermal head that is able to output different heating temperature in the same scanning suitable for a thermal element that develops different colors according to heating temperature for example, particularly relates to a thermal head which is able to reduce the influences of accumulated heat in the thermal head. Furthermore, the present invention relates to a thermal head to which binary data of whether high energy data or low energy data can be serially input.
In case printing is performed on thermosensitive paper by a thermal head, heretofore, printing is performed in fixed color such as black when printing energy (temperature) becomes higher than T0as shown in FIG. 4A and as printing density becomes light and in the case of energy lower than the energy, the thermal head is not heated in a part in which printing is not desired. That is, only control over operation of whether printing is performed or not according to whether data exists on a line or not is executed.
A thermal head to which a history control circuit for limiting the rise of temperature by heat accumulation in a thermal head board is added to control operation also exists, however, the objective is to control so that a thermal head is under single temperature in printing, that is, single energy.
Recently, multi-color thermosensitive paper that a character and others are printed in black for example when a high temperature thermal head is used and they are printed in red for example when a low temperature thermal head is used is manufactured. For example, it is provided as a product name MB-23 manufactured by Oji Paper Co., Ltd (Japan).
That is, this type of thermosensitive paper develops red for example when the printing energy (temperature) of a thermal head is T2as shown in FIG. 4B and develops black when the printing energy is T1(T2 less than T1). When the printing energy becomes further higher than T1, whitening effect occurs. As apparent from FIG. 4B, this type of thermosensitive paper has two developing energy peaks T2and T1for red and black. This type of thermosensitive paper enabling not only the combination of red and black but the combination of other colors according to the degree of printing energy also exists.
In case red and black printing is performed on a scanning line L0as shown in FIG. 5A for example when plural-color printing is performed using such multi-color thermosensitive paper, it is conventionally required to first transfer data to be printed in red by current of quantity corresponding to low temperature and to then transfer data on the same scanning line L0again by current of quantity corresponding to high temperature.
Also, as shown in FIG. 5B, in case red and black two-color printing is performed, data to be printed in red on scanning lines L1, L2, - - - is transferred by current of quantity corresponding to low temperature and then, data on the same scanning lines L1, L2, - - - is transferred by current of quantity corresponding to high temperature.
As described above, to correspond to two types of energy, data is transferred per one line twice and each energy is set. As data is required to be transferred per one line twice, there is a problem that printing speed is slow.
A first object of the present invention is to provide a thermal head which is able to output different heating temperatures corresponding a plural colors in a single scanning to a thermal sensitive medium which develops different colors depending on the heating temperature.
A second object of the present invention is to provide a thermal head in that data to be printed by high energy in the vicinity of data to be printed by low energy was prevented from having an effect upon data to be printed by low energy. A third object of the invention is to provide a thermal head in that the data of a high energy part and the data of a low energy part respectively input to a shift register are not input in parallel but can be serially input to solve the problems.
To achieve the object, the thermal head comprises a first strobe signal input means performing the heating control of a heating means corresponding to first energy, a second strobe signal input means performing the heating control of the heating means corresponding to second energy, a first heating time control means for controlling the heating of the heating means based on the first strobe signal depending on the presence/absence of a print data within a print control range under control of the first energy, and a second heating time control means for controlling the heating of the heating means based on the second strobe signal depending on the presence/absence of a print data within a print control range under control of the second energy.
Further, connecting means may be provided to notify the print data to be printed by first energy to the second heating time control means.
Furthermore, a shift register 100 according to the invention is characterized in that as shown in FIG. 1, first shift register elements 101-1 to 101-n for storing the data of a high energy part are connected in series, second shift register elements 102-1 to 102-n for storing the data of a low energy part are connected in series and the first shift register element 101-n and the second shift register element 102-1 are connected in series.
First, a n-bit data string of a low energy part is input from an input terminal Ti. Hereby, the n-bit data string of the low energy part is held in the first shift register element 101-1, - - - or 101-n. Next, when a n-bit data string of a high energy part is similarly input from the input terminal Ti, the n-bit data string of the low energy part first input is held in the second shift register element 102-1, - - - or 102-n and the data string of the high energy part is held in the first shift register element 101-1, - - - or 101-n.
These data are input to a control circuit shown in FIG. 11 for example as Q1 and q1 and printing processing is executed. As described above, input data can be serially input from the input terminal Ti without being input in parallel.